A soybean variety designated 93B67, the plants and seeds of soybean variety 93B67, methods for producing a soybean plant produced by crossing the variety 93B67 with itself or with another soybean plant, and hybrid soybean seeds and plants produced by crossing the variety 93B67 with another soybean line or plant, and the creation of variants by mutagenesis or transformation of variety 93B67. This invention also relates to methods for producing other soybean varieties or breeding lines derived from soybean variety 93B67 and to soybean varieties or breeding lines produced by those methods.

This invention is in the field of soybean breeding, specifically relating to a soybean variety designated 93B67.
The present invention relates to a new and distinctive soybean variety, designated 93B67 which has been the result of years of careful breeding and selection as part of a soybean breeding program. There are numerous steps in the development of any novel, desirable plant germplasm. Plant breeding begins with the analysis and definition of problems and weaknesses of the current germplasm, the establishment of program goals, and the definition of specific breeding objectives. The next step is selection of germplasm that possess the traits to meet the program goals. The goal is to combine in a single variety an improved combination of desirable traits from the parental germplasm. These important traits may include higher seed yield, resistance to diseases and insects, tolerance to drought and heat, and better agronomic qualities.
Field crops are bred through techniques that take advantage of the plant""s method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is cross-pollinated if the pollen comes from a flower on a different plant. Soybean plants (Glycine max), are recognized to be naturally self-pollinated plants which, while capable of undergoing cross-pollination, rarely do so in nature. Insects are reported by some researchers to carry pollen from one soybean plant to another and it generally is estimated that less than one percent of soybean seed formed in an open planting can be traced to cross-pollination, i.e. less than one percent of soybean seed formed in an open planting is capable of producing F1 hybrid soybean plants, See Jaycox, xe2x80x9cEcological Relationships between Honey Bees and Soybeans,xe2x80x9d appearing in the American Bee Journal Vol. 110(8): 306-307 (August 1970). Thus intervention for control of pollination is critical to establishment of superior varieties.
A cross between two different homozygous lines produces a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform. Regardless of parentage, plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny.
Soybeans, (Glycine max), can be bred by both self-pollination and cross-pollination techniques. Choice of breeding or selection methods depends on the mode of plant reproduction, the heritability of the trait(s) being improved, and the type of variety used commercially (e.g., F1 hybrid variety, pureline variety, etc.). For highly heritable traits, a choice of superior individual plants evaluated at a single location will be effective, whereas for traits with low heritability, selection should be based on mean values obtained from replicated evaluations of families of related plants. Popular selection methods commonly include pedigree selection, modified pedigree selection, mass selection, and recurrent selection.
The complexity of inheritance influences choice of the breeding method. Pedigree breeding and recurrent selection breeding methods are used to develop varieties from breeding populations. Pedigree breeding starts with the crossing of two genotypes, each of which may have one or more desirable characteristics that is lacking in the other or which complements the other. If the two original parents do not provide all the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive generations. In the succeeding generations the heterozygous condition gives way to homogeneous lines as a result of self-pollination and selection. Typically in the pedigree method of breeding five or more generations of selfing and selection is practiced: F1xe2x86x92F2; F2xe2x86x92F3; F3xe2x86x92F4; F4xe2x86x92F5, etc.
Pedigree breeding is commonly used for the improvement of self-pollinating crops. Two parents that possess favorable, complementary traits are crossed to produce an F1. An F2 population is produced by selfing one or several F1""s or by intercrossing two F1""s (sib mating). Selection of the best individuals may begin in the F2 population; then, beginning in the F3, the best individuals in the best families are selected. Replicated testing of families can begin in the F4 generation to improve the effectiveness of selection for traits with low heritability. At an advanced stage of inbreeding (i.e., F6 and F7), the best lines or mixtures of phenotypically similar lines are tested for potential release as new varieties.
Backcross breeding has been used to transfer genes for simply inherited, highly heritable traits into a desirable homozygous variety or inbred line that is utilized as the recurrent parent. The source of the traits to be transferred is called the donor parent. After the initial cross, individuals possessing the desired traits of the donor parent are selected and repeatedly crossed (backcrossed) to the recurrent parent. The resulting plant is expected to have the attributes of the recurrent parent (e.g., variety) and the desirable traits transferred from the donor parent. This approach has been used extensively for breeding disease resistant varieties.
Each soybean breeding program should include a periodic, objective evaluation of the efficiency of the breeding procedure. Evaluation criteria vary depending on the goal and objectives, but should include gain from selection per year based on comparisons to an appropriate standard, overall value of the advanced breeding lines, and number of successful varieties produced per unit of input (e.g., per year, per dollar expended, etc.).
Various recurrent selection techniques are used to improve quantitatively inherited traits controlled by numerous genes. The use of recurrent selection in self-pollinating crops depends on the ease of pollination, the frequency of successful hybrids from each pollination, and the number of hybrid offspring from each successful cross.
Promising advanced breeding lines are thoroughly tested and compared to appropriate standards in environments representative of the commercial target area(s) for three or more years. The best lines are candidates for new commercial varieties; those still deficient in a few traits may be used as parents to produce new populations for further selection.
Publically available or newly-released varieties of soybean can also be used as parental lines or starting materials for breeding or as source populations from which to develop or derive other soybean varieties or breeding lines. These varieties or lines derived from publically available or newly-released varieties can be developed by using breeding methods described earlier, such as pedigree breeding, backcrossing and recurrent selection. As an example, when backcross breeding is used to create these derived lines or varieties in a soybean breeding program, publicly available or newly released varieties of soybeans can be used as a parental line or starting material or source population and can serve as either the donor or recurrent parent. See for example, Fehr, xe2x80x9cBreeding Methods for Cultivar Developmentxe2x80x9d, Chapter 7, Soybeans Improvement, Production and Uses, 2nd ed., Wilcox ed. 1987.
These processes, which lead to the final step of marketing and distribution, can take from eight to twelve years from the time the first cross is made. Therefore, development of new varieties is a time-consuming process that requires precise forward planning, efficient use of resources, and a minimum of changes in direction.
A most difficult task is the identification of individuals that are genetically superior, because for most traits the true genotypic value is masked by other confounding plant traits or environmental factors. One method of identifying a superior plant is to observe its performance relative to other experimental plants and to a widely grown standard variety. Generally a single observation is inconclusive, so replicated observations are required to provide a better estimate of its genetic worth.
In addition to the preceding problem, it is not known how the genotype will react with the environment. This genotype by environment interaction is an important, yet unpredictable, factor in plant breeding. A breeder of ordinary skill in the art cannot predict the genotype, how that genotype will interact with various environments or the resulting phenotypes of the developing lines, except perhaps in a very broad and general fashion. A breeder of ordinary skill in the art would also be unable to recreate the same line twice from the very same original parents, as the breeder is unable to direct how the genomes combine or how they will interact with the environmental conditions. This unpredictability results in the expenditure of large amounts of research resources in the development of a superior new soybean variety.
The goal of soybean breeding is to develop new, unique and superior soybean varieties. In practical application of a chosen soybean breeding program, the breeder initially selects and crosses two or more parental lines, followed by repeated selfing and selection, producing many new genetic combinations. The breeder can theoretically generate billions of different genetic combinations via crossing, selfing and mutations. The breeder has no direct control at the cellular level. Therefore, two breeders will never develop the same line, or even very similar lines, having the same soybean traits.
Each year, the plant breeder selects the germplasm to advance to the next generation. This germplasm is grown under unique and different geographical, climatic and soil conditions, and further selections are then made during and at the end of the growing season. The varieties which are developed are unpredictable for the reasons already mentioned.
Mass and recurrent selections can be used to improve populations of either self-or cross-pollinated crops. A genetically variable population of heterozygous individuals is either identified or created by intercrossing several different parents. The best plants are selected based on individual superiority, outstanding progeny, or excellent combining ability. The selected plants are intercrossed to produce a new population in which further cycles of selection are continued.
The single-seed descent procedure in the strict sense refers to planting a segregating population, harvesting a sample of one seed per plant, and using the one-seed sample to plant the next generation. When the population has been advanced from the F2 to the desired level of inbreeding, the plants from which lines are derived will each trace to different F2 individuals. The number of plants in a population declines each generation due to failure of some seeds to germinate or some plants to produce at least one seed. As a result, not all of the F2 plants originally sampled in the population will be represented by a progeny when generation advance is completed.
In a multiple-seed procedure, soybean breeders commonly harvest one or more pods from each plant in a population and thresh them together to form a bulk. Part of the bulk is used to plant the next generation and part is put in reserve. The procedure has been referred to as modified single-seed descent or the pod-bulk technique.
The multiple-seed procedure has been used to save labor at harvest. It is considerably faster to thresh pods with a machine than to remove one seed from each by hand for the single-seed procedure. The multiple-seed procedure also makes it possible to plant the same number of seeds of a population each generation of inbreeding. Enough seeds are harvested to make up for those plants that did not germinate or produce seed.
Descriptions of other breeding methods that are commonly used for different traits and crops can be found in one of several reference books (e.g., Allard, 1960; Simmonds, 1979; Sneep et al., 1979; Fehr, 1987).
Proper testing should detect major faults and establish the level of superiority or improvement over current varieties. In addition to showing superior performance, there must be a demand for a new variety. The new variety must be compatible with industry standards, or must create a new market. The introduction of a new variety may incur additional costs to the seed producer, the grower, processor and consumer, for special advertising and marketing, altered seed and commercial production practices, and new product utilization. The testing preceding release of a new variety should take into consideration research and development costs as well as technical superiority of the final variety. For seed-propagated varieties, it must be feasible to produce seed easily and economically.
Soybean (Glycine max), is an important and valuable field crop. Thus, a continuing goal of soybean breeders is to develop stable, high yielding soybean varieties that are agronomically sound. The reasons for this goal are obviously to maximize the amount of grain produced on the land used and to supply food for both animals and humans. To accomplish this goal, the soybean breeder must select and develop soybean plants that have the traits that result in superior varieties.
Pioneer soybean research staff create over 500,000 potential new varieties each year. Of those new varieties, less than 50 and more commonly less than 25 are actually selected for commercial use.
According to the invention, there is provided a novel soybean variety, designated 93B67. This invention thus relates to the seeds of soybean variety 93B67, to the plants of soybean 93B67 and to methods for producing a soybean plant produced by crossing soybean variety 93B67 with itself or another soybean plant, and the creation of variants by mutagenesis or transformation of soybean 93B67. This invention also relates to methods for producing other soybean varieties or breeding lines derived from soybean variety 93B67 and to soybean varieties or breeding lines produced by those methods. Soybean variety 93B67 is characterized by a unique combination of yield potential, disease and herbicide resistance for its maturity.
In the description and tables which follow, a number of terms are used. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided:
B/A=BUSHELS PER ACRE. The seed yield in bushels/acre is the actual yield of the grain at harvest.
BSR=BROWN STEM ROT TOLERANCE. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based on leaf symptoms of yellowing and necrosis caused by brown stem rot. A score of 9 indicates no symptoms. Visual scores range down to a score of 1 which indicates severe symptoms of leaf yellowing and necrosis.
CNKR=STEM CANKER TOLERANCE. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon premature plant death. A score of 9 indicates no symptoms, whereas a score of 1 indicates the entire experimental unit died very early.
COTYLEDON. A cotyledon is a type of seed leaf. The cotyledon contains the food storage tissues of the seed.
EMBRYO. The embryo is the small plant contained within a mature seed.
F3. This symbol denotes a generation resulting from the selfing of the F2 generation along with selection for type and rogueing of off-types. The xe2x80x9cFxe2x80x9d number is a term commonly used in genetics, and designates the number of the filial generation. The xe2x80x9cF3xe2x80x9d generation denotes the offspring resulting from the selfing or self mating of members of the generation having the next lower xe2x80x9cFxe2x80x9d number, viz the F2 generation.
FECL=IRON-DEFICIENCY CHLOROSIS. Plants are scored 1 to 9 based on visual observations. A score of 1 indicates the plants are dead or dying from iron-deficiency chlorosis, a score of 5 means plants have intermediate health with some leaf yellowing and a score of 9 means no stunting of the plants or yellowing of the leaves.
FEY=Frogeye Tolerance. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon leaf lesions. A score of 9 indicates no lesions, whereas a score of 1 indicates severe leaf necrosis.
HABIT. This refers to the physical appearance of a plant. It can be either determinate or indeterminate. In soybeans, indeterminate varieties are those in which stem growth is not limited by formation of a reproductive structure (i.e., flowers, pods and seeds) and hence growth continues throughout flowering and during part of pod filling. The main stem will develop and set pods over a prolonged period under favorable conditions. In soybeans, determinate varieties are those in which stem growth ceases at flowering time. Most flowers develop simultaneously, and most pods fill at approximately the same time.
HGT=Plant Height. Plant height is taken from the top of the soil to top pod of the plant and is measured in inches.
HILUM. This refers to the scar left on the seed which marks the place where the seed was attached to the pod prior to it (the seed) being harvested.
HYPL=HYPOCOTYL ELONGATION. This score indicates the ability of the seed to emerge when planted 3xe2x80x3 deep in sand and with a controlled temperature of 25xc2x0 C. The number of plants that emerge each day are counted. Based on this data, each genotype is given a 1 to 9 score based on its rate of emergence and percent of emergence. A score of 9 indicates an excellent rate and percent of emergence, an intermediate score of 5 indicates average ratings and a 1 score indicates a very poor rate and percent of emergence.
HYPOCOTYL. A hypocotyl is the portion of an embryo or seedling between the cotyledons and the root. Therefore, it can be considered a transition zone between shoot and root.
LDG=LODGING RESISTANCE. Lodging is rated on a scale of 1 to 9. A score of 9 indicates erect plants. A score of 5 indicates plants are leaning at a 45xc2x0 angle in relation to the ground and a score of 1 indicates plants are laying on the ground.
LEAFLETS. These are part of the plant shoot, and they manufacture food for the plant by the process of photosynthesis.
LLE=Linoleic Acid Percent. Linoleic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
LLN=Linolenic Acid Percent. Linolenic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
MAT ABS=ABSOLUTE MATURITY. This term is defined as the length of time from planting to complete physiological development (maturity). The period from planting until maturity is reached is measured in days, usually in comparison to one or more standard varieties. Plants are considered mature when 95% of the pods have reached their mature color.
MATURITY GROUP. This refers to an agreed-on industry division of groups of varieties, based on the zones in which they are adapted primarily according to day length or latitude. They consist of very long day length varieties (Groups 000, 00, 0), and extend to very short day length varieties (Groups VII, VIII, IX, X).
OIL=Oil Percent. Soybean seeds contain a considerable amount of oil. Oil is measured by NIR spectrophotometry, and is reported on an as is percentage basis.
OLC=OLEIC ACID PERCENT. Oleic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
PLM=Palmitic Acid Percent. Palmitic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
POD. This refers to the fruit of a soybean plant. It consists of the hull or shell (pericarp) and the soybean seeds.
PRT=PHYTOPHTHORA TOLERANCE. Tolerance to Phytophthora root rot is rated on a scale of 1 to 9, with a score of 9 being the best or highest tolerance ranging down to a score of 1 which indicates the plants have no tolerance to Phytophthora.
PRM=Predicted Relative Maturity. Soybean maturities are divided into relative maturity groups. In the United States the most common maturity groups are 0 through VIII. Within these maturity groups the industry generally divides maturities into tenths of a relative maturity group. Within narrow comparisons, the difference of a tenth of a relative maturity group equates very roughly to a day difference in maturity at harvest.
PRO=Protein Percent. Soybean seeds contain a considerable amount of protein. Protein is generally measured by NIR spectrophotometry, and is reported on an as is percentage basis.
PUBESCENCE. This refers to a covering of very fine hairs closely arranged on the leaves, stems and pods of the soybean plant.
RKA=Root-knot nematode, peanut. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon digging plants to look at the roots for presence or absence of galling. A score of 9 indicates that there is no galling of the roots, a score of 1 indicates large severe galling cover most of the root system which results in pre-mature death from decomposing of the root system.
RKI=Root-knot nematode, southern. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon digging plants to visually score the roots for presence or absence of galling. A score of 9 indicates that there is no galling of the roots, a score of 1 indicates large severe galling cover most of the root system which results in pre-mature death from decomposing of the root system.
SDS=Sudden Death Syndrome. Tolerance to Sudden Death Syndrome is rated on a scale of 1 to 9, with a score of 1 being very susceptible ranging up to a score of 9 being resistant.
S/LB=Seeds per Pound. Soybean seeds vary in seed size, therefore, the number of seeds required to make up one pound also varies. This affects the pounds of seed required to plant a given area, and can also impact end uses.
SH=SHATTERING. This refers to the amount of pod dehiscence prior to harvest. Pod dehiscence involves seeds falling from the pods to the soil. This is a visual score from 1 to 9 comparing all genotypes within a given test. A score of 9 means pods have not opened and no seeds have fallen out. A score of 5 indicates approximately 50% of the pods have opened, with seeds falling to the ground and a score of 1 indicates 100% of the pods are opened.
SHOOTS. These are a portion of the body of the plant. They consist of stems, petioles and leaves.
STC=STEARIC ACID PERCENT. Stearic acid is one of the five most abundant fatty acids in soybean seeds. It is measured by gas chromatography and is reported as a percent of the total oil content.
WH MD=WHITE MOLD TOLERANCE. This is a visual disease score from 1 to 9 comparing all genotypes in a given test. The score is based upon observations of mycelial growth and death of plants. A score of 9 indicates no symptoms. Visual scores of 1 indicate complete death of the experimental unit.
A soybean variety needs to be highly homogeneous, homozygous and reproducible to be useful as a commercial variety. There are many analytical methods available to determine the homozygotic and phenotypic stability of these inbred lines.
The oldest and most traditional method of analysis is the observation of phenotypic traits. The data is usually collected in field experiments over the life of the soybean plants to be examined. Phenotypic characteristics most often observed are for traits associated with seed yield, seed protein and oil content, lodging resistance, disease resistance, maturity, plant height, and shattering.
In addition to phenotypic observations, the genotype of a plant can also be examined. There are many laboratory-based techniques available for the analysis, comparison and characterization of plant genotype; among these are Isozyme Electrophoresis, Restriction Fragment Length Polymorphisms (RFLPs), Randomly Amplified Polymorphic DNAs (RAPDs), Arbitrarily Primed Polymerase Chain Reaction (AP-PCR), DNA Amplification Fingerprinting (DAF), Sequence Characterized Amplified Regions (SCARs), Amplified Fragment Length Polymorphisms (AFLPs), and Simple Sequence Repeats (SSRs) which are also referred to as Microsatellites.
The variety of the invention has shown uniformity and stability for all traits, as described in the following variety description information. It has been self-pollinated a sufficient number of generations, with careful attention to uniformity of plant type to ensure homozygosity and phenotypic stability. The line has been increased with continued observation for uniformity. No variant traits have been observed or are expected in 93B67, as described in Table 1 (Variety Description Information).
Soybean variety 93B67 is a white flowered, soybean variety with tawny pubescence, black hila, and a relative maturity of 36. Variety 93B67 also demonstrates very good yield in combination with Multi-race Phytophthora resistance (Rps1c). 93B67 further demonstrates moderate resistance to Soybean Cyst Nematode, races 3 and 14 and displays a substantial degree of glyphosate resistance. Variety 93B67 is particularly suited to the Plains, Southern Plains and Eastern regions of the United States including Iowa, Illinois, Indiana, and Missouri. This variety may have a narrow width canopy.
Soybean variety 93B67, being substantially homozygous, can be reproduced by planting seeds of the line, growing the resulting soybean plants under self-pollinating or sib-pollinating conditions, and harvesting the resulting seed, using techniques familiar to the agricultural arts.
With the advent of molecular biological techniques that have allowed the isolation and characterization of genes that encode specific protein products, scientists in the field of plant biology developed a strong interest in engineering the genome of plants to contain and express foreign genes, or additional, or modified versions of native, or endogenous, genes (perhaps driven by different promoters) in order to alter the traits of a plant in a specific manner. Such foreign, additional and/or modified genes are referred to herein collectively as xe2x80x9ctransgenesxe2x80x9d. Over the last fifteen to twenty years several methods for producing transgenic plants have been developed, and the present invention, in particular embodiments, also relates to transformed versions of the claimed variety or line.
Plant transformation involves the construction of an expression vector which will function in plant cells. Such a vector comprises DNA comprising a gene under control of or operatively linked to a regulatory element (for example, a promoter). The expression vector may contain one or more such operably linked gene/regulatory element combinations. The vector(s) may be in the form of a plasmid, and can be used alone or in combination with other plasmids, to provide transformed soybean plants, using transformation methods as described below to incorporate transgenes into the genetic material of the soybean plant(s).
Marker Genes
Expression vectors include at least one.genetic marker, operably linked to a regulatory element (a promoter, for example) that allows transformed cells containing the marker to be either recovered by negative selection, i.e. inhibiting growth of cells that do not contain the selectable marker gene, or by positive selection, i.e., screening for the product encoded by the genetic marker. Many commonly used selectable marker genes for plant transformation are well known in the transformation arts, and include, for example, genes that code for enzymes that metabolically detoxify a selective chemical agent which may be an antibiotic or a herbicide, or genes that encode an altered target which is insensitive to the inhibitor. A few positive selection methods are also known in the art.
One commonly used selectable marker gene for plant transformation is the neomycin phosphotransferase II (nptII) gene, isolated from transposon Tn5, which when placed under the control of plant regulatory signals confers resistance to kanamycin. Fraley et al., Proc. Natl. Acad. Sci. U.S.A., 80: 4803 (1983). Another commonly used selectable marker gene is the hygromycin phosphotransferase gene which confers resistance to the antibiotic hygromycin. Vanden Elzen et al., Plant Mol. Biol., 5: 299 (1985).
Additional selectable marker genes of bacterial origin that confer resistance to antibiotics include gentamycin acetyl transferase, streptomycin phosphotransferase, aminoglycoside-3xe2x80x2-adenyl transferase, the bleomycin resistance determinant. Hayford et al., Plant Physiol. 86: 1216 (1988), Jones et al., Mol. Gen. Genet., 210: 86 (1987), Svab et al., Plant Mol. Biol. 14: 197 (1990), Hille et al., Plant Mol. Biol. 7: 171 (1986). Other selectable marker genes confer resistance to herbicides such as glyphosate, glufosinate or broxynii. Comai et al., Nature 317: 741-744 (1985), Gordon-Kamm et al., Plant Cell 2: 603-618 (1990) and Stalker et al., Science 242: 419423 (1988).
Other selectable marker genes for plant transformation are not of bacterial origin. These genes include, for example, mouse dihydrofolate reductase, plant 5-enolpyruvylshikimate-3-phosphate synthase and plant acetolactate synthase. Eichholtz et al., Somatic Cell Mol. Genet. 13: 67 (1987), Shah et al., Science 233: 478 (1986), Charest et al., Plant Cell Rep. 8: 643 (1990).
Another class of marker genes for plant transformation require screening of presumptively transformed plant cells rather than direct genetic selection of transformed cells for resistance to a toxic substance such as an antibiotic. These genes are particularly useful to quantify or visualize the spatial pattern of expression of a gene in specific tissues and are frequently referred to as reporter genes because they can be fused to a gene or gene regulatory sequence for the investigation of gene expression. Commonly used genes for screening presumptively transformed cells include xcex2-glucuronidase (GUS), xcex2-galactosidase, luciferase and chloramphenicol acetyltransferase. Jefferson, R. A., Plant Mol. Biol. Rep. 5: 387 (1987)., Teeri et al., EMBO J. 8: 343 (1989), Koncz et al., Proc. Natl. Acad. Sci. U.S.A. 84:131 (1987), De Block et al., EMBO J. 3: 1681 (1984).
Recently, in vivo methods for visualizing GUS activity that do not require destruction of plant tissue have been made available. Molecular Probes Publication 2908, Imagene Green(trademark), p. 1-4 (1993) and Naleway et al., J. Cell Biol. 115: 15Ia (1991). However, these in vivo methods for visualizing GUS activity have not proven useful for recovery of transformed cells because of low sensitivity, high fluorescent backgrounds and limitations associated with the use of luciferase genes as selectable markers.
More recently, a gene encoding Green Fluorescent Protein (GFP) has been utilized as a marker for gene expression in prokaryotic and eukaryotic cells. Chalfie et al., Science 263: 802 (1994). GFP and mutants of GFP may be used as screenable markers.
Genes included in expression vectors must be driven by a nucleotide sequence comprising a regulatory element, for example, a promoter. Several types of promoters are now well known in the transformation arts, as are other regulatory elements that can be used alone or in combination with promoters. As used herein xe2x80x9cpromoterxe2x80x9d includes reference to a region of DNA upstream from the start of transcription and involved in recognition and binding of RNA polymerase and other proteins to initiate transcription. A xe2x80x9cplant promoterxe2x80x9d is a promoter capable of initiating transcription in plant cells. Examples of promoters under developmental control include promoters that preferentially initiate transcription in certain tissues, such as leaves, roots, seeds, fibers, xylem vessels, tracheids, or sclerenchyma. Such promoters are referred to as xe2x80x9ctissue-preferredxe2x80x9d. Promoters which initiate transcription only in certain tissue are referred to as xe2x80x9ctissue-specificxe2x80x9d. A xe2x80x9ccell typexe2x80x9d specific promoter primarily drives expression in certain cell types in one or more organs, for example, vascular cells in roots or leaves. An xe2x80x9cinduciblexe2x80x9d promoter is a promoter which is under environmental control. Examples of environmental conditions that may effect transcription by inducible promoters include anaerobic conditions or the presence of light. Tissue-specific, tissue-preferred, cell type specific, and inducible promoters constitute the class of xe2x80x9cnon-constitutivexe2x80x9d promoters. A xe2x80x9cconstitutivexe2x80x9d promoter is a promoter which is active under most environmental conditions.
A. Inducible Promoters
An inducible promoter is operably linked to a gene for expression in soybean. Optionally, the inducible promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in soybean. With an inducible promoter the rate of transcription increases in response to an inducing agent.
Any inducible promoter can be used in the instant invention. See Ward et al. Plant Mol. Biol.22: 361-366 (1993). Exemplary inducible promoters include, but are not limited to, that from the ACEI system which responds to copper (Mett et al. PNAS 90: 4567-4571 (1993)); In2 gene from maize which responds to benzenesulfonamide herbicide safeners (Hershey et al., Mol. Gen. Genetics 227: 229-237 (1991) and Gatz et al., Mol. Gen. Genetics 243: 32-38 (1994)) or Tet repressor from Tn10 (Gatz et al., Mol. Gen. Genet. 227: 229-237 (1991). A particularly preferred inducible promoter is a promoter that responds to an inducing agent to which plants do not normally respond. An exemplary inducible promoter is the inducible promoter from a steroid hormone gene, the transcriptional activity of which is induced by a glucocorticosteroid hormone. Schena et al., Proc. Natl. Acad. Sci. U.S.A. 88: 0421 (1991).
B. Constitutive Promoters
A constitutive promoter is operably linked to a gene for expression in soybean or the constitutive promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in soybean.
Many different constitutive promoters can be utilized in the instant invention. Exemplary constitutive promoters include, but are not limited to, the promoters from plant viruses such as the 35S promoter from CaMV (Odell et al., Nature 313: 810-812 (1985) and the promoters from such genes as rice actin (McElroy et al., Plant Cell 2: 163-171 (1990)); ubiquitin (Christensen et al., Plant Mol. Biol.12: 619-632 (1989) and Christensen et al., Plant Mol. Biol. 18: 675-689 (1992)); pEMU (Last et al., Theor. Appl. Genet. 81: 581-588 (1991)); MAS (Velten et al., EMBO J. 3: 2723-2730 (1984)) and maize H3 histone (Lepetit et al., Mol. Gen. Genet.231: 276-285 (1992) and Atanassova et al., Plant Journal 2 (3): 291-300 (1992)).
The ALS promoter, a XbaI/NcoI fragment 5xe2x80x2 to the Brassica napus ALS3 structural gene (or a nucleotide sequence that has substantial sequence similarity to said XbaI/NcoI fragment), represents a particularly useful constitutive promoter. See PCT application WO96/30530.
C. Tissue-specific or Tissue-preferred Promoters
A tissue-specific promoter is operably linked to a gene for expression in soybean. Optionally, the tissue-specific promoter is operably linked to a nucleotide sequence encoding a signal sequence which is operably linked to a gene for expression in soybean. Plants transformed with a gene of interest operably linked to a tissue-specific promoter produce the protein product of the transgene exclusively, or preferentially, in a specific tissue.
Any tissue-specific or tissue-preferred promoter can be utilized in the instant invention. Exemplary tissue-specific or tissue-preferred promoters include, but are not limited to, a root-preferred promoter such as that from the phaseolin gene (Murai et al., Science 23: 476-482 (1983) and Sengupta-Gopalan et al., Proc. Natl. Acad. Sci. USA 82: 3320-3324 (1985)); a leaf-specific and light-induced promoter such as that from cab or rubisco (Simpson et al., EMBO J. 4(11): 2723-2729 (1985) and Timko et al., Nature 318: 579-582 (1985)); an anther-specific promoter such as that from LAT52 (Twell et al., Mol. Gen. Genet 217: 240-245 (1989)); a pollen-specific promoter such as that from Zm13 (Guerrero et al., Mol. Gen. Genet. 224: 161-168 (1993)) or a microspore-preferred promoter such as that from apg (Twell et al., Sex. Plant Reprod. 6: 217-224 (1993).
Transport of protein produced by transgenes to a subcellular compartment such as the chloroplast, vacuole, peroxisome, glyoxysome, cell wall or mitochondrion, or for secretion into the apoplast, is accomplished by means of operably linking the nucleotide sequence encoding a signal sequence to the 5xe2x80x2 and/or 3xe2x80x2 region of a gene encoding the protein of interest. Targeting sequences at the 5xe2x80x2 and/or 3xe2x80x2 end of the structural gene may determine, during protein synthesis and processing, where the encoded protein is ultimately compartmentalized.
The presence of a signal sequence directs a polypeptide to either an intracellular organelle or subcellular compartment or for secretion to the apoplast. Many signal sequences are known in the art. See, for example, Becker et al., Plant Mol. Biol.20: 49 (1992), Close, P. S., Master""s Thesis, Iowa State University (1993), Knox, C., et al., xe2x80x9cStructure and Organization of Two Divergent Alpha-Amylase Genes From Barleyxe2x80x9d, Plant Mol.Biol. 9: 3-17 (1987), Lerner et al., Plant Physiol. 91: 124-129 (1989), Fontes et al., Plant Cell 3: 483496 (1991), Matsuoka et al., Proc. Natl. Acad. Sci. 88: 834 (1991), Gould et al., J. Cell Biol 108: 1657 (1989), Creissen et al., Plant J. 2: 129 (1991), Kalderon, D., Robers, B., Richardson, W., and Smith A., xe2x80x9cA short amino acid sequence able to specify nuclear locationxe2x80x9d, Cell 39: 499-509 (1984), Stiefel, V., Ruiz-Avila, L., Raz R., Valles M., Gomez J., Pages M., Martinez-Izquierdo J., Ludevid M., Landale J., Nelson T., and Puigdomenech P., xe2x80x9cExpression of a maize cell wall hydroxyproline-rich glycoprotein gene in early leaf and root vascular differentiationxe2x80x9d, Plant Cell 2: 785-793 (1990).
With transgenic plants according to the present invention, a foreign protein can be produced in commercial quantities. Thus, techniques for the selection and propagation of transformed plants, which are well understood in the art, yield a plurality of transgenic plants which are harvested in a conventional manner, and a foreign protein then can be extracted from a tissue of interest or from total biomass. Protein extraction from plant biomass can be accomplished by known methods which are discussed, for example, by Heney and Orr, Anal. Biochem. 114: 92-6 (1981).
According to a preferred embodiment, the transgenic plant provided for commercial production of foreign protein is a soybean plant. In another preferred embodiment, the biomass of interest is seed. For the relatively small number of transgenic plants that show higher levels of expression, a genetic map can be generated, primarily via conventional RFLP, PCR, and SSR analysis, which identifies the approximate chromosomal location of the integrated DNA molecule. For exemplary methodologies in this regard, see Glick and Thompson, METHODS IN PLANT MOLECULAR BIOLOGY AND BIOTECHNOLOGY 269-284 (CRC Press, Boca Raton, 1993). Map information concerning chromosomal location is useful for proprietary protection of a subject transgenic plant. If unauthorized propagation is undertaken and crosses made with other germplasm, the map of the integration region can be compared to similar maps for suspect plants, to determine if the latter have a common parentage with the subject plant. Map comparisons would involve hybridizations, RFLP, PCR, SSR and sequencing, all of which are conventional techniques.
Likewise, by means of the present invention, agronomic genes can be expressed in transformed plants. More particularly, plants can be genetically engineered to express various phenotypes of agronomic interest. Exemplary genes implicated in this regard include, but are not limited to, those categorized below.
1. Genes That Confer Resistance to Pests or Disease and That Encode:
(A) Plant disease resistance genes. Plant defenses are often activated by specific interaction between the product of a disease resistance gene (R) in the plant and the product of a corresponding avirulence (Avr) gene in the pathogen. A plant variety can be transformed with cloned resistance gene to engineer plants that are resistant to specific pathogen strains. See, for example Jones et al., Science 266: 789 (1994) (cloning of the tomato Cf-9 gene for resistance to Cladosporium fulvum); Martin et al., Science 262: 1432 (1993) (tomato Pto gene for resistance to Pseudomonas syringae pv. tomato encodes a protein kinase); Mindrinos et al., Cell 78: 1089 (1994) (Arabidopsis RSP2 gene for resistance to Pseudomonas syringae).
(B) A gene conferring resistance to a pest, such as soybean cyst nematode. See e.g. PCT Application WO96/30517; PCT Application WO93119181.
(C) A Bacillus thuringiensis protein, a derivative thereof or a synthetic polypeptide modeled thereon. See, for example, Geiser et al., Gene 48: 109 (1986), who disclose the cloning and nucleotide sequence of a Bt xcex4-endotoxin gene. Moreover, DNA molecules encoding xcex4-endotoxin genes can be purchased from American Type Culture Collection (Manassas, Va.), for example, under ATCC Accession Nos. 40098, 67136, 31995 and 31998.
(D) A lectin. See, for example, the disclosure by Van Damme et al., Plant Molec. Biol. 24: 25 (1994), who disclose the nucleotide sequences of several Clivia miniata mannose-binding lectin genes.
(E) A vitamin-binding protein such as avidin. See PCT application US93/06487, the contents of which are hereby incorporated by reference. The application teaches the use of avidin and avidin homologues as larvicides against insect pests.
(F) An enzyme inhibitor, for example, a protease or proteinase inhibitor or an amylase inhibitor. See, for example, Abe et al., J. Biol. Chem. 262: 16793 (1987) (nucleotide sequence of rice cysteine proteinase inhibitor), Huub et al., Plant Molec. Biol. 21: 985 (1993) (nucleotide sequence of cDNA encoding tobacco proteinase inhibitor I), Sumitani et al., Biosci. Biotech. Biochem. 57: 1243 (1993) (nucleotide sequence of Streptomyces nitrosporeus xcex1-amylase inhibitor) and U.S. Pat. No. 5,494,813 (Hepher and Atkinson, issued Feb. 27, 1996).
(G) An insect-specific hormone or pheromone such as an ecdysterbid and juvenile hormone, a variant thereof, a mimetic based thereon, or an antagonist or agonist thereof. See, for example, the disclosure by Hammock et al., Nature 344: 458 (1990), of baculovirus expression of cloned juvenile hormone esterase, an inactivator of juvenile hormone.
(H) An insect-specific peptide or neuropeptide which, upon expression, disrupts the physiology of the affected pest. For example, see the disclosures of Regan, J. Biol. Chem. 269: 9 (1994) (expression cloning yields DNA coding for insect diuretic hormone receptor), and Pratt et al., Biochem. Biophys. Res. Comm. 163: 1243 (1989) (an allostatin is identified in Diploptera puntata). See also U.S. Pat. No. 5,266,317 to Tomalski et al., who disclose genes encoding insect-specific, paralytic neurotoxins.
(I) An insect-specific venom produced in nature by a snake, a wasp, etc. For example, see Pang et al., Gene 116: 165 (1992), for disclosure of heterologous expression in plants of a gene coding for a scorpion insectotoxic peptide.
(J) An enzyme responsible for an hyperaccumulation of a monterpene, a sesquiterpene, a steroid, hydroxamic acid, a phenylpropanoid derivative or another non-protein molecule with insecticidal activity.
(K) An enzyme involved in the modification, including the post-translational modification, of a biologically active molecule; for example, a glycolytic enzyme, a proteolytic enzyme, a lipolytic enzyme, a nuclease, a cyclase, a transaminase, an esterase, a hydrolase, a phosphatase, a kinase, a phosphorylase, a polymerase, an elastase, a chitinase and a glucanase, whether natural or synthetic. See PCT application WO 93/02197 in the name of Scott et al., which discloses the nucleotide sequence of a callase gene. DNA molecules which contain chitinase-encoding sequences can be obtained, for example, from the ATCC under Accession Nos. 39637 and 67152. See also Kramer et al., Insect Biochem. Molec. Biol. 23: 691 (1993), who teach the nucleotide sequence of a cDNA encoding tobacco hookworm chitinase, and Kawalleck et al., Plant Molec. Biol. 21: 673 (1993), who provide the nucleotide sequence of the parsley ubi4-2 polyubiquitin gene.
(L) A molecule that stimulates signal transduction. For example, see the disclosure by Botella et al., Plant Molec. Biol. 24: 757 (1994), of nucleotide sequences for mung bean calmodulin cDNA clones, and Griess et al., Plant Physiol.104: 1467 (1994), who provide the nucleotide sequence of a maize calmodulin cDNA clone.
(M) A hydrophobic moment peptide. See PCT application WO95/16776 (disclosure of peptide derivatives of Tachyplesin which inhibit fungal plant pathogens) and PCT application WO95/18855 (teaches synthetic antimicrobial peptides that confer disease resistance), the respective contents of which are hereby incorporated by reference.
(N) A membrane permease, a channel former or a channel blocker. For example, see the disclosure by Jaynes et al., Plant Sci. 89: 43 (1993), of heterologous expression of a cecropin-xcex2 lytic peptide analog to render transgenic tobacco plants resistant to Pseudomonas solanacearum.
(O) A viral-invasive protein or a complex toxin derived therefrom. For example, the accumulation of viral coat proteins in transformed plant cells imparts resistance to viral infection and/or disease development effected by the virus from which the coat protein gene is derived, as well as by related viruses. See Beachy et al., Ann. Rev. Phytopathol.28: 451 (1990). Coat protein-mediated resistance has been conferred upon transformed plants against alfalfa mosaic virus, cucumber mosaic virus, tobacco streak virus, potato virus X, potato virus Y, tobacco etch virus, tobacco rattle virus and tobacco mosaic virus. Id.
(P) An insect-specific antibody or an immunotoxin derived therefrom. Thus, an antibody targeted to a critical metabolic function in the insect gut would inactivate an affected enzyme, killing the insect. Cf. Taylor et al., Abstract #497, SEVENTH INT""L SYMPOSIUM ON MOLECULAR PLANT-MICROBE INTERACTIONS (Edinburgh, Scotland, 1994) (enzymatic inactivation in transgenic tobacco via production of single-chain antibody fragments).
(Q) A virus-specific antibody. See, for example, Tavladoraki et al., Nature 366: 469 (1993), who show that transgenic plants expressing recombinant antibody genes are protected from virus attack.
(R) A developmental-arrestive protein produced in nature by a pathogen or a parasite. Thus, fungal endo xcex1-1,4-D-polygalacturonases facilitate fungal colonization and plant nutrient release by solubilizing plant cell wall homo-xcex1-1,4-D-galacturonase. See Lamb et al., Bio/Technology 10: 1436 (1992). The cloning and characterization of a gene which encodes a bean endopolygalacturonase-inhibiting protein is described by Toubart et al., Plant J. 2: 367 (1992).
(S) A developmental-arrestive protein produced in nature by a plant. For example, Logemann et al., Bio/Technology 10: 305 (1992), have shown that transgenic plants expressing the barley ribosome-inactivating gene have an increased resistance to fungal disease.
2. Genes That Confer Resistance to a Herbicide, for Example:
(A) A herbicide that inhibits the growing point or meristem, such as an imidazalinone or a sulfonylurea. Exemplary genes in this category code for mutant ALS and AHAS enzyme as described, for example, by Lee et al., EMBO J. 7: 1241 (1988), and Miki et al., Theor. Appl.Genet. 80: 449 (1990), respectively.
(B) Glyphosate (resistance imparted by mutant 5-enolpyruvl-3-phosphikimate synthase (EPSP) and aroA genes, respectively) and other phosphono compounds such as glufosinate (phosphinothricin acetyl transferase, PAT) and Streptomyces hygroscopicus phosphinothricin-acetyl transferase, bar, genes), and pyridinoxy or phenoxy propionic acids and cycloshexones (ACCase inhibitor-encoding genes). See, for example, U.S. Pat. No. 4,940,835 to Shah et al., which discloses the nucleotide sequence of a form of EPSP which can confer glyphosate resistance. A DNA molecule encoding a mutant aroA gene can be obtained under ATCC accession No. 39256, and the nucleotide sequence of the mutant gene is disclosed in U.S. Pat. No. 4,769,061 to Comai. European patent application No. 0 333 033 to Kumada et al. and U.S. Pat. No. 4,975,374 to Goodman et al. disclose nucleotide sequences of glutamine synthetase genes which confer resistance to herbicides such as L-phosphinothricin. The nucleotide sequence of a phosphinothricin-acetyl-transferase gene is provided in European application No. 0 242 246 to Leemans et al. De Greef et al., Bio/Technology 7: 61 (1989), describe the production of transgenic plants that express chimeric bar genes coding for phosphinothricin acetyl transferase activity. Exemplary of genes conferring resistance to phenoxy -propionic acids and cycloshexones, such as sethoxydim and haloxyfop, are the Acc1-S1, Acc1-S2 and Acc1-S3 genes described by Marshall et al., Theor. Appl. Genet. 83: 435 (1992).
(C) A herbicide that inhibits photosynthesis, such as a triazine (psbA and gs+ genes) and a benzonitrile (nitrilase gene). Przibilla et al., Plant Cell 3: 169 (1991), describe the transformation of Chlamydomonas with plasmids encoding mutant psbA genes. Nucleotide sequences for nitrilase genes are disclosed in U.S. Pat. No. 4,810,648 to Stalker, and DNA molecules containing these genes are available under ATCC Accession Nos. 53435, 67441 and 67442. Cloning and expression of DNA coding for a glutathione S-transferase is described by Hayes et al., Biochem. J. 285: 173 (1992).
3. Genes That Confer or Contribute to a Value-added Trait, Such as:
(A) Modified fatty acid metabolism, for example, by transforming a plant with an antisense gene of stearoyl-ACP desaturase to increase stearic acid content of the plant. See Knultzon et al., Proc. Natl. Acad. Sci. USA 89: 2624 (1992).
(B) Decreased phytate content
(1) Introduction of a phytase-encoding gene would enhance breakdown of phytate, adding more free phosphate to the transformed plant. For example, see Van Hartingsveldt et al., Gene 127: 87 (1993), for a disclosure of the nucleotide sequence of an Aspergillus niger phytase gene.
(2) A gene could be introduced that reduces phytate content. In maize, this, for example, could be accomplished, by cloning and then reintroducing DNA associated with the single allele which is responsible for maize mutants characterized by low levels of phytic acid. See Raboy et al., Maydica 35: 383 (1990).
(C) Modified carbohydrate composition effected, for example, by transforming plants with a gene coding for an enzyme that alters the branching pattern of starch. See Shiroza et al., J. Bacteriol. 170: 810 (1988) (nucleotide sequence of Streptococcus mutans fructosyltransferase gene), Steinmetz et al., Mol. Gen. Genet. 200: 220 (1985) (nucleotide sequence of Bacillus subtilis levansucrase gene), Pen et al., Bio/Technology 10: 292 (1992) (production of transgenic plants that express Bacillus licheniformis xcex1-amylase), Elliot et al., Plant Molec. Biol. 21: 515 (1993) (nucleotide sequences of tomato invertase genes), Sxc3x8gaard et al., J. Biol. Chem. 268: 22480 (1993) (site-directed mutagenesis of barley xcex1-amylase gene), and Fisher et al., Plant Physiol. 102: 1045 (1993) (maize endosperm starch branching enzyme II).
Numerous methods for plant transformation have been developed, including biological and physical, plant transformation protocols. See, for example, Miki et al., xe2x80x9cProcedures for Introducing Foreign DNA into Plantsxe2x80x9d in Methods in Plant Molecular Biology and Biotechnology, Glick, B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 67-88. In addition, expression vectors and in vitro culture methods for plant cell or tissue transformation and regeneration of plants are available. See, for example, Gruber et al., xe2x80x9cVectors for Plant Transformationxe2x80x9d in Methods in Plant Molecular Biology and Biotechnology, Glick, B. R. and Thompson, J. E. Eds. (CRC Press, Inc., Boca Raton, 1993) pages 89-119.
A. Agrobacterum-mediated Transformation
One method for introducing an expression vector into plants is based on the natural transformation system of Agrobacterium. See, for example, Horsch et al., Science 227: 1229 (1985). A. tumefaciens and A. rhizogenes are plant pathogenic soil bacteria which genetically transform plant cells. The Ti and Ri plasmids of A. tumefaciens and A. rhizogenes, respectively, carry genes responsible for genetic transformation of the plant. See, for example, Kado, C. I., Crit. Rev. Plant. Sci.10: 1 (1991). Descriptions of Agrobacterium vector systems and methods for Agrobacterium-mediated gene transfer are provided by Gruber et al., supra, Miki et al., supra, and Moloney et al., Plant Cell Reports 8: 238 (1989). See also, U.S. Pat. No. 5,563,055, (Townsend and Thomas), issued Oct. 8, 1996.
B. Direct Gene Transfer
Several methods of plant transformation, collectively referred to as direct gene transfer, have been developed as an alternative to Agrobacterium-mediated transformation. A generally applicable method of plant transformation is microprojectile-mediated transformation wherein DNA is carried on the surface of microprojectiles measuring 1 to 4 xcexcm. The expression vector is introduced into plant tissues with a biolistic device that accelerates the microprojectiles to speeds of 300 to 600 m/s which is sufficient to penetrate plant cell walls and membranes. Sanford et al., Part. Sci. Technol. 5: 27 (1987), Sanford, J. C., Trends Biotech. 6: 299 (1988), Klein et al, Bio/Technology 6: 559-563 (1988), Sanford, J. C., Physiol Plant 79: 206 (1990), Klein et al, Biotechnology 10: 268 (1992). See also U.S. Pat. No. 5,015,580 (Christou, et al.), issued May 14, 1991; U.S. Pat. No. 5,322,783 (Tomes, et al.), issued Jun. 21, 1994.
Another method for physical delivery of DNA to plants is sonication of target cells. Zhang et al., Bio/Technology 9: 996 (1991). Alternatively, liposome or spheroplast fusion have been used to introduce expression vectors into plants. Deshayes et al., EMBO J., 4: 2731 (1985), Christou et al., Proc Natl. Acad. Sci. U.S.A. 84: 3962 (1987). Direct uptake of DNA into protoplasts using CaCl2 precipitation, polyvinyl alcohol or poly-L-ornithine have also been reported. Hain et al., Mol. Gen. Genet.199: 161 (1985) and Draper et al., Plant Cell Physiol.23: 451 (1982). Electroporation of protoplasts and whole cells and tissues have also been described. Donn et al., In Abstracts of VIIth International Congress on Plant Cell and Tissue Culture IAPTC, A2-38, p 53 (1990); D""Halluin et al., Plant Cell 4: 1495-1505 (1992) and Spencer et al., Plant Mol. Biol. 24: 51-61 (1994).
Following transformation of soybean target tissues, expression of the above-described selectable marker genes allows for preferential selection of transformed cells, tissues and/or plants, using regeneration and selection methods now well known in the art.
The foregoing methods for transformation would typically be used for producing a transgenic variety. The transgenic variety could then be crossed, with another (non-transformed or transformed) variety, in order to produce a new transgenic variety. Alternatively, a genetic trait which has been engineered into a particular soybean line using the foregoing transformation techniques could be moved into another line using traditional backcrossing techniques that are well known in the plant breeding arts. For example, a backcrossing approach could be used to move an engineered trait from a public, non-elite variety into an elite variety, or from a variety containing a foreign gene in its genome into a variety or varieties which do not contain that gene. As used herein, xe2x80x9ccrossingxe2x80x9d can refer to a simple X by Y cross, or the process of backcrossing, depending on the context.
Further reproduction of the variety can occur by tissue culture and regeneration. Tissue culture of various tissues of soybeans and regeneration of plants therefrom is well known and widely published. For example, reference may be had to Komatsuda, T. et al., xe2x80x9cGenotype X Sucrose Interactions for Somatic Embryogenesis in Soybean,xe2x80x9d Crop Sci. 31:333-337 (1991); Stephens, P. A. et al., xe2x80x9cAgronomic Evaluation of Tissue-Culture-Derived Soybean Plants,xe2x80x9d Theor. Appl. Genet. (1991) 82:633-635; Komatsuda, T. et al., xe2x80x9cMaturation and Germination of Somatic Embryos as Affected by Sucrose and Plant Growth Regulators in Soybeans Glycine gracilis Skvortz and Glycine max (L.) Merr.,xe2x80x9d Plant Cell, Tissue and Organ Culture, 28:103-113 (1992); Dhir, S. et al., xe2x80x9cRegeneration of Fertile Plants from Protoplasts of Soybean (Glycine max L. Merr.): Genotypic Differences in Culture Response,xe2x80x9d Plant Cell Reports (1992) 11:285-289; Pandey, P. et al., xe2x80x9cPlant Regeneration from Leaf and Hypocotyl Explants of Glycine wightii (W. and A.) VERDC. var. longicauda,xe2x80x9d Japan J. Breed. 42:1-5 (1992); and Shetty, K., et al., xe2x80x9cStimulation of In Vitro Shoot Organogenesis in Glycine max (Merrill.) by Allantoin and Amides,xe2x80x9d Plant Science 81: (1992) 245-251; as well as U.S. Pat. No. 5,024,944, issued Jun. 18, 1991 to Collins et al. and U.S. Pat. No. 5,008,200, issued Apr. 16, 1991 to Ranch et al., the disclosures of which are hereby incorporated herein in their entirety by reference. Thus, another aspect of this invention is to provide cells which upon growth and differentiation produce soybean plants having the physiological and morphological characteristics of soybean variety 93B67.
This invention also is directed to methods for producing a soybean plant by crossing a first parent soybean plant with a second parent soybean plant wherein the first or second parent soybean plant is a soybean plant of the variety 93B67. Further, both first and second parent soybean plants can come from the soybean variety 93B67. Thus, any such methods using the soybean variety 93B67 are part of this invention: selfing, backcrosses, hybrid production, crosses to populations, and the like. All plants produced using soybean variety 93B67 as a parent are within the scope of this invention, including those developed from varieties derived from soybean variety 93B67. Advantageously, the soybean variety could be used in crosses with other, different, soybean plants to produce first generation (F1) soybean hybrid seeds and plants with superior characteristics. The variety of the invention can also be used for transformation where exogenous genes are introduced and expressed by the variety of the invention. Genetic variants created either through traditional breeding methods using variety 93B67 or through transformation of 93B67 by any of a number of protocols known to those of skill in the art are intended to be within the scope of this invention.
As used herein, the term plant includes plant cells, plant protoplasts, plant cell tissue cultures from which soybean plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as embryos, pollen, ovules, seed, flowers, pods, leaves, roots, root tips, anthers, and the like.
The seed of soybean variety 93B67, the plant produced from the seed, the hybrid soybean plant produced from the crossing of the variety with any other soybean plant, hybrid seed, and various parts of the hybrid soybean plant can be utilized for human food, livestock feed, and as a raw material in industry.
The soybean is the world""s leading source of vegetable oil and protein meal. The oil extracted from soybeans is used for cooking oil, margarine, and salad dressings. Soybean oil is composed of saturated, monounsaturated and polyunsaturated fatty acids. It has a typical composition of 11% palmitic, 4% stearic, 25% oleic, 50% linoleic and 9% linolenic fatty acid content (xe2x80x9cEconomic Implications of Modified Soybean Traits Summary Reportxe2x80x9d, Iowa Soybean Promotion Board and American Soybean Association Special Report 92S, May 1990). Changes in fatty acid composition for improved oxidative stability and nutrition are constantly sought after. Industrial uses of soybean oil which is subjected to further processing include ingredients for paints, plastics, fibers, detergents, cosmetics, and lubricants. Soybean oil may be split, inter-esterified, sulfurized, epoxidized, polymerized, ethoxylated, or cleaved. Designing and producing soybean oil derivatives with improved functionality, oliochemistry, is a rapidly growing field. The typical mixture of triglycerides is usually split and separated into pure fatty acids, which are then combined with petroleum-derived alcohols or acids, nitrogen, sulfonates, chlorine, or with fatty alcohols derived from fats and oils.
Soybean is also used as a food source for both animals and humans. Soybean is widely used as a source of protein for animal feeds for poultry, swine and cattle. During processing of whole soybeans, the fibrous hull is removed and the oil is extracted. The remaining soybean meal is a combination of carbohydrates and approximately 50% protein.
For human consumption soybean meal is made into soybean flour which is processed to protein concentrates used for meat extenders or specialty pet foods. Production of edible protein ingredients from soybean offers a healthy, less expensive replacement for animal protein in meats as well as dairy-type products.


A flame-retarded polyolefin fiber made of a thermoplastic polyolefin and a graft copolymer composition represented by tile formula: ##STR1## in which PP is polypropylene, and S represents grafted side chains having halogenated monomeric units of the formula: ##STR2## wherein x=1 to 4, R.sub.8 is H or CH.sub.3, R.sub.9 is H or a C.sub.1-4 alkyl group, and R.sub.10 is Br or Cl. In an alternate embodiment the flame-retarded polyolefin fiber further includes a halogenated bisphenol derivative represented by the formula: ##STR3## in which R.sub.1 to R.sub.4 are H, CH.sub.3 or a halogen, R.sub.5 is H, dihaloethyl, dihalopropyl or dihalobutyl, and A is a single bond, O, CO, S, SO.sub.2 or C(R.sub.6)(R.sub.7), where R.sub.6 and R.sub.7 are H or a C.sub.1-4 alkyl.

1. Field of the Invention
The present invention relates generally to flame-retarded fibers, and more particularly to flame-retarded, polyolefin-based fibers. The inventive flame-retarded fibers are comprised of a thermoplastic polyolefin and a ring halogenated vinyl aromatic grafted onto a polyolefin, and may also include a halogenated bisphenol derivative.
2. Description of the Prior Art
Polyolefin fibers--predominantly polyethylene and polypropylene--are high volume/low cost synthetics that are remarkable for their stain and abrasion resistance. As with all plastics, certain uses have required that the flammability of the polymer be reduced. When decreased flammability has been required, it has generally not been provided by the fiber itself, but has instead been provided by one of the other components in the fabricated article. In carpeting, for example, enough fire retardant can be loaded into the latex binder to provide a measure of protection for the polyolefin face fiber.
One reason why the fiber itself has not been formulated to contain fire retarding agents is that no fire retarding agent has been found which leaves the fiber with an acceptable balance of normal polyolefin properties. In addition, the presence of an additive often adversely affects the melt spinning operation. For example, hexabromocyclododecane ("HBCD") can be compounded into polypropylene and the blend melt extruded into fibers. To be economical, however, the fiber must be produced at as high a rate as possible. This requires that melt viscosity be reduced by raising the die temperature. Unfortunately, normal processing temperatures for polypropylene cause degradation of HBCD and impart an unacceptable brown color to the fiber.
Many attempts have been made to produce acceptable ignition resistant polyolefin fibers and fabrics. Much of this work has focused on topical applications in which flame retarding agents were coated onto the surface of fibers after the fibers had been produced. Permanence was not always assured, as often the active ingredient was merely dispersed in a polymeric binder which was "painted" onto the polyolefin fiber. The quality of the binder determined the longevity of the treatment.
More sophisticated topical methods utilized phosphorus- or halogen-based monomers which were applied to the fiber and crosslinked in place. While providing ignition resistance, these approaches change the feel or "hand" of the fabric and reduce a key property of the polyolefins--soil resistance.
An important limitation of topical applications is that they are restricted to use with spun fiber, or more commonly, with constructed fabrics. They cannot be applied to the resin prior to--or what would be the most efficient, during --the fiber spinning operation. Topical applications therefore require an additional and costly step in the production process.
Other attempts to provide flame retardancy employ an "additive" approach. Almost any non-volatile compound containing bromine or chlorine may be mixed into polyolefins to provide some measure of ignition resistance. None has been successfully commercialized due to problems with the strength, color, odor or toxicity of the fiber.
One problem with known flame retardant additives is the difficulty of effectively dispersing them into the molten polyolefin. Additives are generally powders which do not dry blend evenly with plastic pellets. Because this mixture is fed directly from the melt extruder to the spinning die, localized concentrations of undispersed flame retardant will occur. This will cause plugging of the spinnerette and filament breakage, requiring a shutdown of tile process. One solution is to pre-disperse the additives in a suitable thermoplastic resin to form concentrated plastic pellets containing the modifiers. This solution, of course, requires additional and costly steps in the production process.
To avoid the problems associated with additives, attempts have been made to chemically bond modifiers to the polyolefin molecule to provide ignition resistant fibers. In one process, elemental chlorine and bromine are attached to the surface molecules of polyolefin fibers and films to provide self-extinguishing behavior. Similarly, the grafting of vinylchloride or vinylidene chloride to the surface of polyolefin fibers in order to obtain diminished flammability is known. As with the topical applications, these grafting approaches suffered from the limitation that they could only be applied as post-treatments, requiring additional steps in the production process.
Polyolefin fibers containing non-halogenated styrene grafted to polypropylene have also been manufactured. In one method, polypropylene-g-styrene is co-spun with polypropylene to produce a highly crimped fiber with good tensile strength. Similarly, the grafting of styrene onto pre-formed polypropylene fibers is known. In one method, a halo styrene in the form of chloromethylstyrene is grafted to polypropylene fiber to produce a material with improved sticking temperature, color fastness, water retention, antistatic behavior and wool-like hand with uniform dyeability. None of these methods provides adequate flame retardancy while retaining reasonable textile properties. Also, these approaches are generally limited to post-treatment of the fiber and therefore include the previously-discussed disadvantages incumbent therewith.
Concerning bromostyrene graft copolymers specifically, U.S. Pat. No. 5,077,337 to Atwell et al. discloses graft copolymers represented by the formula: ##STR4## in which n is an integer >1; P is a polyolefin; and S is a side chain grafted to the polypropylene and having monomeric units of the formula: ##STR5## in which x=1 to 4; R.sub.1 is H or CH.sub.3 ; and R.sub.2 is H or a C.sub.1-4 alkyl, and notes that such graft copolymers would be an improvement over inert additives in the production of flame retardant spun fibers because clogging of spinnerettes and equipment wear would be avoided.
A need therefore exists for a polyolefin fiber which melts into the base polyolefin under normal spinning conditions leaving no solid particles to plug spinnerettes. A need also exists for a polyolefin fiber which is thermally stable, non-topical, non-blooming, non-volatile, UV stable, dry blendable and spinnable into 2 to 3 dpf microfibers without extra compounding steps. Also, a need exists for such a fiber which further does not impart objectionable odors to the spun fiber or constructed fabrics made thereof, and which has essentially the same texture or hand as nonflame-retarded fibers. Finally, a need exists for such a fiber which is further insoluble in water and is evenly distributed throughout the fiber to make it extremely resistant to removal by normal laundering conditions. The present invention addresses these needs.

Fire retardant polyolefin fibers and fabrics